Go into a game store and ask for a D21, or the illogical D3 (asking for a D3 can result in them giveing you a D6 with sides numbered 1,1,2,2,3,3 or giveing you a D6 telling you to divide any number larger than 3 by 2)
Or ask for a D0.

"some people are like slinkies there really good for nothing, but they still bring a smile to your face when you push them down a flight of stairs""Triangalism! What's the fuckin' point!"